In order to fix a tubular door lock, it is necessary to cut a long opening from the side surface of a door so as to fit a dead bolt in and a circular opening through two sides of the door a suitable distance from the edge of the side surface so as to fit a knob in for moving the dead bolt. Since the size of posts used in doors are not unified, carpenters need to cut an opening at different distances according to the variety of the door. Therefore, the door lock manufacturers have to prepare more molds for making different sizes of locks and retailers have to own more space for storing them. Moreover, the consumers must as well have the knowledge about the locks should they want to buy locks of proper sizes. In order to save the above-mentioned inconveniences, the inventor has devise a tubular door lock with an adjustable device for setting the dead bolt.